Field of the Invention
The present invention relates to an electrophotographic member, a developing apparatus and an image forming apparatus using electrophotography.
Description of the Related Art
Users of image forming apparatuses using electrophotography have demanded formation of electrophotographic images less degradable after long-term use and a small change over time in the quality of the formed electrophotographic images. To produce such high quality electrophotographic images, preventing adhesion of toners to non-image portions (hereinafter, referred to as “fogging”) is essential. The term “fogging” indicates a phenomenon in which a developer is charged to a charging polarity opposite to that to which the developer is originally charged, so that the developer adheres to non-image portions which should not be developed. The developer charged to the polarity opposite to that to which the developer is originally charged is hereinafter also referred to as “reversal developer.”
To prevent such “fogging,” the developing member should have high charging properties to prevent generation or a reversal developer, and have a high electric resistance such that the charge of the charged developer is not decayed until development. To prevent “fogging,” the charging member should have charging properties such that after completion of the transfer step, the reversal polarity of the reversal developer remaining on the photosensitive member can be charged to the original polarity to return the developer from the photosensitive member to the developing unit. These properties of the charging member are particularly useful in photosensitive members having no cleaning mechanism. In such photosensitive members having no cleaning mechanism, all of the developer remaining on the photosensitive, member without being transferred passes through the charging member, and cannot be returned to the developing unit. As result, the residual developer is unintentionally disposed on the non-image portions in the next developing step to generate fogging.
To meet the requirements on the developing member and the charging member described above, the developer adhering to the surfaces of these members is an obstacle in demonstration of the effects to be provided by these members. For this reason, high lubrication is also required to prevent adhesion of the developer to the surfaces of these members. Japanese Patent Application Laid-Open No. 2012-83595 discloses a developing member including a surface layer including a compound having a Si—O—Sr bond or a Si—O—Ta bond to have a dense crosslinked structure and have high lubrication.